A. Field of the Invention
The present invention relates to an ink ribbon of a high-speed printer used for data processing of computers, or more particularly, to a mechanism for preventing slack in an ink ribbon. A stopper is provided which engages or disengages with a lever for preventing the backward movement of the ratchet wheel on which a spool of the ink ribbon is mounted . This prevents slack of the ink ribbon when the ink ribbon is fed, stablizes the feeding of the ink ribbon and improves the printing quality.
B. Description of the Prior Art
In an ink ribbon feed mechanism of a high-speed printer, the ink ribbon is stretched between a pair of ratchet wheels on which a spool of the ink ribbon is mounted, and the ink ribbon is fed when needed for printing. In the prior art mechanism, a back-stopper for preventing backward movement of the ink ribbon is provided only at the take-up side of the ratchet wheel. Therefore, at the supply side of the ink ribbon, the slack of the ink ribbon occurs when the ink ribbon is fed or reversed on account of the friction between the ink ribbon and the printing paper as well as the printing position. The printing quality correspondingly deteriorates and also the life of the ink ribbon is reduced. To prevent this slack, a high degree of friction is applied to the supply side of the ratchet wheel. But due to the friction, the necessary power input for turning the above-said ratchet wheel is required to be increased, and the mechanism for averaging the friction is complicated.